/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package io.grpc.internal;

import com.alipay.sofa.jraft.util.internal.ReferenceFieldUpdater;
import com.alipay.sofa.jraft.util.internal.Updaters;
import io.grpc.ForwardingServerCall;
import io.grpc.ServerCall;

/**
 * Get grpc's server stream.
 *
 * @author jiachun.fjc
 */
public class ServerStreamHelper {

    private static final ReferenceFieldUpdater<ServerCallImpl<?, ?>, ServerStream>                                      STREAM_GETTER      = Updaters
                                                                                                                                               .newReferenceFieldUpdater(
                                                                                                                                                   ServerCallImpl.class,
                                                                                                                                                   "stream");

    private static final ReferenceFieldUpdater<ForwardingServerCall.SimpleForwardingServerCall<?, ?>, ServerCall<?, ?>> SERVER_CALL_GETTER = Updaters
                                                                                                                                               .newReferenceFieldUpdater(
                                                                                                                                                   ForwardingServerCall.SimpleForwardingServerCall.class,
                                                                                                                                                   "delegate");

    public static ServerStream getServerStream(final ServerCall<?, ?> call) {
        ServerCall<?, ?> lastServerCall = call;
        if (call instanceof ForwardingServerCall.SimpleForwardingServerCall) {
            lastServerCall = SERVER_CALL_GETTER.get((ForwardingServerCall.SimpleForwardingServerCall<?, ?>) call);
        }
        if (lastServerCall instanceof ServerCallImpl) {
            return STREAM_GETTER.get((ServerCallImpl<?, ?>) lastServerCall);
        }
        return null;
    }
}
